Cooperation and operation of macro node and remote radio head deployments in heterogeneous networks

ABSTRACT

A method, an apparatus, and a computer program product for wireless communication are provided for separating control transmissions and data transmissions within the coverage area of a plurality of transmission/reception points or points that are geographically displaced, the plurality of points comprising a macro node and a plurality of remote radio heads (RRHs) coupled to the macro node. Separating control transmissions and data transmissions in the macro node/RRH configuration may allow UEs to be associated with one set of transmission points for data transmissions and the same set or a different set of transmission points for common control signaling. Separating control transmissions and data transmissions may also allow for faster reconfiguration of antenna ports used for UE data transmission compared with reconfiguration via a handover process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/442,129, entitled “COOPERATION AND OPERATION OF MACRO AND REMOTERADIO HEAD DEPLOYMENTS IN HETEROGENEOUS NETWORKS” and filed on Feb. 11,2011, the benefit of U.S. Provisional Application Ser. No. 61/442,690,entitled “COOPERATION AND OPERATION OF MACRO AND REMOTE RADIO HEADDEPLOYMENTS IN HETEROGENEOUS NETWORKS” and filed on Feb. 14, 2011, andthe benefit of U.S. Provisional Application Ser. No. 61/442,087,entitled “METHOD AND APPARATUS FOR ENABLING CHANNEL AND INTERFERENCEESTIMATIONS IN MACRO/RRH SYSTEM” and filed on Feb. 11, 2011, which areexpressly incorporated by reference herein in their entirety.

BACKGROUND

1. Field

The present disclosure relates generally to communication systems, andmore particularly, to a cooperation and operation of macro node andremote radio head (RRH) deployments in heterogeneous networks.

2. Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE). LTE is a set ofenhancements to the Universal Mobile Telecommunications System (UMTS)mobile standard promulgated by Third Generation Partnership Project(3GPP). It is designed to better support mobile broadband Internetaccess by improving spectral efficiency, lower costs, improve services,make use of new spectrum, and better integrate with other open standardsusing OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), andmultiple-input multiple-output (MIMO) antenna technology. However, asthe demand for mobile broadband access continues to increase, thereexists a need for further improvements in LTE technology. Preferably,these improvements should be applicable to other multi-accesstechnologies and the telecommunication standards that employ thesetechnologies.

SUMMARY

The disclosure provides for the separation of control transmissions anddata transmissions within a coverage area of a macro node andgeographically displaced remote radio heads (RRHs) coupled to the macronode. The macro node together with the RRHs may be considered aplurality of transmission/reception points (TxPs) or points. Byseparating control and data in the macro node/RRH configuration, userequipments (UEs) may be associated with at least one transmission pointfor data transmission while control information is transmitted based oncommon reference signals (CRS) from a different set of transmissionpoints. This enables cell splitting for data transmissions acrossdifferent transmission points while possibly leaving controltransmissions common for all transmission points. Separating control anddata may allow for faster reconfiguration of antenna ports used for UEdata transmission compared with reconfiguration via a handover process.The separation of control transmissions and data transmissions withinthe coverage of the macro node/RRH configuration may be enabled byUE-specific reference signals.

In an aspect of the disclosure, a method, an apparatus, and a computerprogram product for wireless communication are provided. The apparatusmay include a macro node and at least one remote radio head (RRH)coupled to the macro node, the macro node and the at least one RRHcomprising a plurality of points that are geographically displaced. Theapparatus transmits control information with common reference signals(CRS) to a user equipment (UE) from a first subset of points, and sendsa data transmission based on UE-specific demodulation reference signals(DM-RS) to the UE from a second subset of points.

Another aspect relates to the apparatus transmitting control informationwith common reference signals (CRS) to a user equipment (UE) from asubset of points, receiving a sounding reference signal (SRS) from theUE at one or more points of the plurality of points, determining channelstrengths to each of the one or more points from the UE based on the SRSreceived by the one or more points, determining whether the UE is inclose proximity to at least one point of the one or more points based onthe determined channel strengths, and sending a data transmission basedon CRS to the UE from the at least one point when the UE is determinedto be in close proximity to the at least one point based on thedetermined channel strengths, wherein the data transmission based on CRSis sent to the UE from the at least one point independent of datatransmissions from points not in close proximity to the UE.

A further aspect relates to an apparatus communicating with a macro nodeand at least one remote radio head (RRH) coupled to the macro node, themacro node and the at least one RRH comprising a plurality of pointsthat are geographically displaced. The apparatus is configured forreceiving control information with common reference signals (CRS) from afirst subset of points, receiving data transmitted based on demodulationreference signals (DM-RS) from a second subset of points, receivingchannel state information reference signals (CSI-RS) from the secondsubset of points, and transmitting a channel state information reportbased at least in part on the received CSI-RS, the channel stateinformation report comprising at least one of precoding matrix indicator(PMI), rank index (RI), or channel quality indicator (CQI) feedback.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure inLTE.

FIG. 4 is a diagram illustrating an example of an UL frame structure inLTE.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control planes.

FIG. 6 is a diagram illustrating an example of an evolved Node B anduser equipment in an access network.

FIG. 7 is a diagram illustrating a cellular range expansion (CRE) regionin a heterogeneous network.

FIG. 8 is a diagram illustrating a heterogeneous network with low powerRRHs operating within the same cell region.

FIG. 9 illustrates diagrams of reference signal configurations within aset of resource blocks.

FIG. 10 is a flow chart of a method of wireless communication.

FIG. 11 is a flow chart of a method of wireless communication.

FIG. 12 is a flow chart of a method of wireless communication.

FIG. 13 is a flow chart of a method of wireless communication.

FIG. 14 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 15 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 16 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 17 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, modules, components,circuits, steps, processes, algorithms, etc. (collectively referred toas “elements”). These elements may be implemented using electronichardware, computer software, or any combination thereof. Whether suchelements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented with a “processing system”that includes one or more processors. Examples of processors includemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate arrays (FPGAs), programmable logic devices(PLDs), state machines, gated logic, discrete hardware circuits, andother suitable hardware configured to perform the various functionalitydescribed throughout this disclosure. One or more processors in theprocessing system may execute software. Software shall be construedbroadly to mean instructions, instruction sets, code, code segments,program code, programs, subprograms, software modules, applications,software applications, software packages, routines, subroutines,objects, executables, threads of execution, procedures, functions, etc.,whether referred to as software, firmware, middleware, microcode,hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functionsdescribed may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on or encoded as one or more instructions or code on acomputer-readable medium. Computer-readable media includes computerstorage media. Storage media may be any available media that can beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

FIG. 1 is a diagram illustrating an LTE network architecture 100. TheLTE network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS)120, and an Operator's IP Services 122. The EPS can interconnect withother access networks, but for simplicity those entities/interfaces arenot shown. As shown, the EPS provides packet-switched services, however,as those skilled in the art will readily appreciate, the variousconcepts presented throughout this disclosure may be extended tonetworks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108.The eNB 106 provides user and control planes protocol terminationstoward the UE 102. The eNB 106 may be connected to the other eNBs 108via an X2 interface (e.g., backhaul). The eNB 106 may also be referredto as a base station, a base transceiver station, a radio base station,a radio transceiver, a transceiver function, a basic service set (BSS),an extended service set (ESS), or some other suitable terminology. TheeNB 106 provides an access point to the EPC 110 for a UE 102. Examplesof UEs 102 include a cellular phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a personal digital assistant (PDA), asatellite radio, a global positioning system, a multimedia device, avideo device, a digital audio player (e.g., MP3 player), a camera, agame console, or any other similar functioning device. The UE 102 mayalso be referred to by those skilled in the art as a mobile station, asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client, or someother suitable terminology.

The eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110includes a Mobility Management Entity (MME) 112, other MMEs 114, aServing Gateway 116, and a Packet Data Network (PDN) Gateway 118. TheMME 112 is the control node that processes the signaling between the UE102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theServing Gateway 116, which itself is connected to the PDN Gateway 118.The PDN Gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN Gateway 118 is connected to the Operator's IPServices 122. The Operator's IF Services 122 may include the Internet,the Intranet, an IP Multimedia Subsystem (IMS), and a PS StreamingService (PSS).

FIG. 2 is a diagram illustrating an example of an access network 200 inan LTE network architecture. In this example, the access network 200 isdivided into a number of cellular regions (cells) 202. One or more lowerpower class eNBs 208 may have cellular regions 210 that overlap with oneor more of the cells 202. A lower power class eNB 208 may be, forexample, a remote radio head (RRH). Alternatively, the lower power classeNB 208 may be a femto cell (e.g., home eNB (HeNB)), pico cell, or microcell. The macro eNBs 204 are each assigned to a respective cell 202 andare configured to provide an access point to the EPC 110 for all the UEs206 in the cells 202. There is no centralized controller in this exampleof an access network 200, but a centralized controller may be used inalternative configurations. The eNBs 204 are responsible for all radiorelated functions including radio bearer control, admission control,mobility control, scheduling, security, and connectivity to the servinggateway 116.

The modulation and multiple access scheme employed by the access network200 may vary depending on the particular telecommunications standardbeing deployed. In LTE applications, OFDM is used on the DL and SC-FDMAis used on the UL to support both frequency division duplexing (FDD) andtime division duplexing (TDD). As those skilled in the art will readilyappreciate from the detailed description to follow, the various conceptspresented herein are well suited for LTE applications. However, theseconcepts may be readily extended to other telecommunication standardsemploying other modulation and multiple access techniques. By way ofexample, these concepts may be extended to Evolution-Data Optimized(EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interfacestandards promulgated by the 3rd Generation Partnership Project 2(3GPP2) as part of the CDMA2000 family of standards and employs CDMA toprovide broadband Internet access to mobile stations. These concepts mayalso be extended to Universal Terrestrial Radio Access (UTRA) employingWideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA;Global System for Mobile Communications (GSM) employing TDMA; andEvolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSMare described in documents from the 3GPP organization. CDMA2000 and UMBare described in documents from the 3GPP2 organization. The actualwireless communication standard and the multiple access technologyemployed will depend on the specific application and the overall designconstraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. Theuse of MIMO technology enables the eNBs 204 to exploit the spatialdomain to support spatial multiplexing, beamforming, and transmitdiversity. Spatial multiplexing may be used to transmit differentstreams of data simultaneously on the same frequency. The data steamsmay be transmitted to a single UE 206 to increase the data rate or tomultiple UEs 206 to increase the overall system capacity. This isachieved by spatially precoding each data stream (i.e., applying ascaling of an amplitude and a phase) and then transmitting eachspatially precoded stream through multiple transmit antennas on the DL.The spatially precoded data streams arrive at the UE(s) 206 withdifferent spatial signatures, which enables each of the UE(s) 206 torecover the one or more data streams destined for that UE 206. On theUL, each UE 206 transmits a spatially precoded data stream, whichenables the eNB 204 to identify the source of each spatially precodeddata stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork will be described with reference to a MIMO system supportingOFDM on the DL. OFDM is a spread-spectrum technique that modulates dataover a number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames.Each sub-frame may include two consecutive time slots. A resource gridmay be used to represent two time slots, each time slot including aresource block. The resource grid is divided into multiple resourceelements. In LTE, a resource block contains 12 consecutive subcarriersin the frequency domain and, for a normal cyclic prefix in each OFDMsymbol, 7 consecutive OFDM symbols in the time domain, or 84 resourceelements. For an extended cyclic prefix, a resource block contains 6consecutive OFDM symbols in the time domain and has 72 resourceelements. Some of the resource elements, as indicated as R 302, 304,include DL reference signals (DL-RS). The DL-RS include Cell-specific RS(CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS)304. UE-RS 304 are transmitted only on the resource blocks upon whichthe corresponding physical DL shared channel (PDSCH) is mapped. Thenumber of bits carried by each resource element depends on themodulation scheme. Thus, the more resource blocks that a UE receives andthe higher the modulation scheme, the higher the data rate for the UE.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein LTE. The available resource blocks for the UL may be partitioned intoa data section and a control section. The control section may be formedat the two edges of the system bandwidth and may have a configurablesize. The resource blocks in the control section may be assigned to UEsfor transmission of control information. The data section may includeall resource blocks not included in the control section. The UL framestructure results in the data section including contiguous subcarriers,which may allow a single UE to be assigned all of the contiguoussubcarriers in the data section.

A UE may be assigned resource blocks 410 a, 410 b in the control sectionto transmit control information to an eNB. The UE may also be assignedresource blocks 420 a, 420 b in the data section to transmit data to theeNB. The UE may transmit control information in a physical UL controlchannel (PUCCH) on the assigned resource blocks in the control section.The UE may transmit only data or both data and control information in aphysical UL shared channel (PUSCH) on the assigned resource blocks inthe data section. A UL transmission may span both slots of a subframeand may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve UL synchronization in a physical random access channel(PRACH) 430. The PRACH 430 carries a random sequence and cannot carryany UL data/signaling. Each random access preamble occupies a bandwidthcorresponding to six consecutive resource blocks. The starting frequencyis specified by the network. That is, the transmission of the randomaccess preamble is restricted to certain time and frequency resources.There is no frequency hopping for the PRACH. The PRACH attempt iscarried in a single subframe (1 ms) or in a sequence of few contiguoussubframes and a UE can make only a single PRACH attempt per frame (10ms).

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in LTE. The radio protocolarchitecture for the UE and the eNB is shown with three layers: Layer 1,Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer andimplements various physical layer signal processing functions. The L1layer will be referred to herein as the physical layer 506. Layer 2 (L2layer) 508 is above the physical layer 506 and is responsible for thelink between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the eNB on the network side. Although not shown, the UEmay have several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between eNBs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 510 provides multiplexing between logical and transportchannels. The MAC sublayer 510 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNBis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the eNB andthe UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650in an access network. In the DL, upper layer packets from the corenetwork are provided to a controller/processor 675. Thecontroller/processor 675 implements the functionality of the L2 layer.In the DL, the controller/processor 675 provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to the UE650 based on various priority metrics. The controller/processor 675 isalso responsible for HARQ operations, retransmission of lost packets,and signaling to the UE 650.

The transmit (TX) processor 616 implements various signal processingfunctions for the L1 layer (i.e., physical layer). The signal processingfunctions includes coding and interleaving to facilitate forward errorcorrection (FEC) at the UE 650 and mapping to signal constellationsbased on various modulation schemes (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded andmodulated symbols are then split into parallel streams. Each stream isthen mapped to an OFDM subcarrier, multiplexed with a reference signal(e.g., pilot) in the time and/or frequency domain, and then combinedtogether using an Inverse Fast Fourier Transform (IFFT) to produce aphysical channel carrying a time domain OFDM symbol stream. The OFDMstream is spatially precoded to produce multiple spatial streams.Channel estimates from a channel estimator 674 may be used to determinethe coding and modulation scheme, as well as for spatial processing. Thechannel estimate may be derived from a reference signal and/or channelcondition feedback transmitted by the UE 650. Each spatial stream isthen provided to a different antenna 620 via a separate transmitter618TX. Each transmitter 618TX modulates an RF carrier with a respectivespatial stream for transmission.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 656. The RX processor 656 implements various signalprocessing functions of the L1 layer. The RX processor 656 performsspatial processing on the information to recover any spatial streamsdestined for the UE 650. If multiple spatial streams are destined forthe UE 650, they may be combined by the RX processor 656 into a singleOFDM symbol stream. The RX processor 656 then converts the OFDM symbolstream from the time-domain to the frequency domain using a Fast FourierTransform (FFT). The frequency domain signal comprises a separate OFDMsymbol stream for each subcarrier of the OFDM signal. The symbols oneach subcarrier, and the reference signal, is recovered and demodulatedby determining the most likely signal constellation points transmittedby the eNB 610. These soft decisions may be based on channel estimatescomputed by the channel estimator 658. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 610 on the physical channel. Thedata and control signals are then provided to the controller/processor659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the control/processor 659 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the eNB 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by the eNB 610.The controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by the eNB 610 may be used by the TXprocessor 668 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar tothat described in connection with the receiver function at the UE 650.Each receiver 618RX receives a signal through its respective antenna620. Each receiver 618RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 670. The RXprocessor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. Thecontroller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, the control/processor 675 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the UE 650. Upper layer packets fromthe controller/processor 675 may be provided to the core network. Thecontroller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

FIG. 7 is a diagram 700 illustrating a cellular range expansion (CRE)region in a heterogeneous network. A heterogeneous network may include amacro node interconnected with a plurality of low power pico nodesoperating within the same cell region. The macro node may beinterconnected with the plurality of pico nodes by an X2 backhaul or anoptical fiber backhaul. When the macro node is interconnected to theplurality of pico nodes via the X2 backhaul, the macro node does nothandle scheduling for the pico nodes. Rather, the low power pico nodesindependently schedule themselves, as scheduling is performed at eachcell. Moreover, the macro node and pico nodes are all configured withdifferent cell identifiers (IDs). The heterogeneous networkinterconnected via the X2 backhaul may use enhanced inter-cellinterference coordination (eICIC) over the backhaul, or other forms ofeICIC, or some form of coordinated multipoint transmission/reception(CoMP), including but not limited to coordinated beamforming, jointtransmission, or distributed antenna selection.

A lower power class eNB such as the RRH 710 b may have a range expandedcellular region 703 that is expanded from the cellular region 702through enhanced inter-cell interference coordination between the RRH710 b and the macro eNB 710 a and through interference cancellationperformed by the UE 720. In enhanced inter-cell interferencecoordination, the RRH 710 b receives information from the macro eNB 710a regarding an interference condition of the UE 720. The informationallows the RRH 710 b to serve the UE 720 in the range expanded cellularregion 703 and to accept a handoff of the UE 720 from the macro eNB 710a as the UE 720 enters the range expanded cellular region 703.

FIG. 8 is a diagram 800 illustrating a heterogeneous network with lowpower RRHs operating within the same cell region 820. In FIG. 8, the lowpower RRHs 804, 806, 808, 810 are interconnected with a macro node 802by an optical fiber 815. Alternatively, the macro node 802 may be a piconode. In general, heterogeneous network setups may provide the mostperformance benefit to advanced UEs (e.g., UEs for LTE Rel-10 or later)when the UEs receive a data transmission from the RRHs or nodes. A keydifference between heterogeneous network setups is related to controlsignaling and handling of legacy impact (e.g., impact on UEs prior toLTE Rel-10).

In an aspect, the macro node 802 handles all scheduling within the cell,for itself and the RRHs 804, 806, 808, 810. The RRHs 804, 806, 808, 810may be configured with the same cell identifier (ID) as the macro node802. If the RRHs 804, 806, 808, 810 are configured with the same cell IDas the macro node 802, the macro node 802 and the RRHs 804, 806, 808,810 essentially operate as one cell controlled by the macro node 802.

The deployment of the macro node 802 and RRHs 804, 806, 808, 810 in FIG.8 may be viewed as a distributed antenna array setup. Concentratedprocessing at the macro node 802 may provide performance benefits.Furthermore, if the RRHs 804, 806, 808, 810 are configured with the samecell ID as the macro node 802, a single CRS may be used, e.g., the samepilot/RS is transmitted from the macro node 802 and each RRH.

In another aspect, the RRHs 804, 806, 808, 810 may be configured with acell identifier (ID) different from the macro node 802. Moreover, eachof the RRHs 804, 806, 808, 810 may be configured with a different cellID, respectively. If the macro node 802 and the RRHs 804, 806, 808, 810are configured with different cell IDs, the macro node 802 and the RRHs804, 806, 808, 810 operate to appear as different cells to a UE,although all control and scheduling may still be handled by the macronode 802. Furthermore, if the macro node 802 and the RRHs 804, 806, 808,810 are configured with different cell IDs, different CRS may be used,e.g., different pilots/RS are transmitted from the macro node 802 andeach RRH.

Referring to FIG. 8, the heterogeneous network interconnected via theoptical fiber backhaul may use enhanced inter-cell interferencecoordination (eICIC) over the backhaul, or other forms of eICIC, or someform of coordinated multipoint transmission/reception (CoMP), includingbut not limited to coordinated beamforming, joint transmission, ordistributed antenna selection. Furthermore, the network of FIG. 8interconnected via the optical fiber backhaul may be considered aheterogeneous network with a perfect backhaul. Perfect backhaultypically refers to an idealized backhaul link that offers sufficientlylow latency and sufficiently high capacity to support the aforementionedoperation. CoMP refers to a wide range of different techniques thatenable dynamic coordination of transmission and/or reception withmultiple geographically separated eNBs or points with the aim to enhanceoverall system performance, utilize resources more effectively, andimprove end-user service quality. Accordingly, when a UE is at acell-edge region, the UE may be able to receive signals from multiplepoints regardless of a system load. With respect to downlinktransmissions, if the signaling transmitted from the multiple points iscoordinated, then downlink performance may be significantly increased.For example, the coordination may focus on interference avoidance orscheduling transmissions of the same data from the multiple eNBs. Withrespect to uplink, a UE signal can be received by the multiple eNBs.Therefore, if scheduling is coordinated from the multiple eNBs, themultiple reception can be taken advantage of to significantly improvelink performance.

FIG. 9 illustrates diagrams 900, 902, and 904 of reference signalconfigurations within a set of resource blocks. The set of resourceblocks may include common or cell-specific reference signals (CRS) forports 1, 2, 3, and 4, demodulation reference signals (DM-RS), andchannel state information reference signals (CSI-RS). Diagram 900 showsa configuration for 2 CSI-RS, diagram 902 shows a configuration for 4CSI-RS, and diagram 904 shows a configuration for 8 CSI-RS. A physicaldownlink control channel (PDCCH) and the PDSCH are also shown.

Referring to FIGS. 8 and 9, each of the RRHs may be assigned to transmiton one or more CSI-RS resources. In general, the macro node and RRHs maybe assigned a subset of a certain CSI-RS resource. For example, for an8-port CSI-RS resource, RRH 1304 may be assigned to transmit on CSI-RSports 0, 1, RRH 806 may be assigned to transmit on CSI-RS ports 2, 3,RRH 808 may be assigned to transmit on CSI-RS ports 4, 5, and RRH 810may be assigned to transmit on CSI-RS ports 6, 7. The macro node and/orRRHs may be assigned the same CSI-RS resources. For example, RRH 804 andRRH 808 may be assigned to transmit on CSI-RS ports 0, 1, 2, 3, and RRH806 and RRH 810 may be assigned to transmit on CSI-RS ports 4, 5, 6, 7.In such a configuration, the CSI-RS from RRHs 804, 808 would overlap andthe CSI-RS from RRHs 806, 810 would overlap.

The configuration of CSI-RS resources is UE-specific. Each UE can beconfigured with a set of CSI-RS resources and each resource may includea predetermined number of CSI-RS ports (e.g., 1, 2, 4, or 8 CSI-RSports). Each UE may receive CSI-RS from one or more of the RRHs 804,806, 808, 810. For example, the UE 822 may receive CSI-RS on CSI-RSports 0, 1 from RRH 804, CSI-RS on CSI-RS ports 2, 3 from RRH 806,CSI-RS on CSI-RS ports 4, 5 from RRH 808, and CSI-RS on CSI-RS ports 6,7 from RRH 810. Such a configuration is specific to the UE 822, as theUE 820 may receive CSI-RS on different ports from the same RRHs.

In another example, the UE 820 may also be configured with 8 CSI-RSports and receive CSI-RS on CSI-RS ports 0, 1 from RRH 808, CSI-RS onCSI-RS ports 2, 3 from RRH 810, CSI-RS on CSI-RS ports 4, 5 from RRH804, and CSI-RS on CSI-RS ports 6, 7 from RRH 806. Generally, for anyparticular UE, the CSI-RS ports may be distributed among the RRHs, andthe particular UE can be configured to receive CSI-RS on those ports,from RRHs configured to send information on those ports to theparticular UE.

When each of the RRHs share the same cell D with the macro node 802,control information may be transmitted with CRS from the macro node orboth the macro node 802 and all of the RRHs. The CRS may be transmittedfrom all of the points (i.e., macro node, RRHs) using the same resourceelements, resulting in the transmitted signals being on top of eachother. Moreover, when all of the points have the same cell ID, the UEmay not be able to differentiate between the CRSs transmitted from eachof the points.

When the RRHs have different cell IDs, the CRS transmitted from each ofthe RRHs may collide. When CRS collision occurs, the CRS from differentcells may be transmitted using the same resource elements. Furthermore,when the RRHs have different cell IDs and the CRS collide, the CRStransmitted from each of the points can be differentiated byinterference cancellation techniques and/or advanced receiverprocessing.

Referring to FIG. 8, when CRS is transmitted from multiple points,proper antenna virtualization may be needed if there are an unequalnumber of physical antennas at the macro node 802 and the RRHs 804, 806,808, 810. That is, CRS should be transmitted from an equal number of(virtual) transmit antennas at each macro node and RRH. For example, ifthe macro node 802 and the RRHs 804, 806, 808 each have four physicalantennas and the RRH 810 has two physical antennas, a first antenna ofthe RRH 810 may be configured to transmit using two CRS ports and asecond antenna of the RRH 810 may be configured to transmit using adifferent two CRS ports. The number of antenna ports can be increased ordecreased in relation to the number of physical antennas.

As discussed supra, the macro node 802 and the RRHs 804, 806, 808, 810may all transmit CRS. However, if only the macro node 802 transmits CRS,a transmission/reception outage can occur close to an RRH nottransmitting CRS due to automatic gain control (AGC) issues.

A difference between heterogeneous network setups using a same cell IDversus different cell IDs for the RRHs is mainly related to controlsignaling, CRS-based transmission modes, and other potential operationsrelying on CRS. The heterogeneous network setup with the different cellIDs and colliding CRS may be advantageous compared to the heterogeneousnetwork setup with the same cell ID because systemcharacteristics/components which depend on the cell ID (e.g., scramblingsequences, etc.) can be more easily differentiated.

When the macro node and the RRHs are configured with the same cell IDand some UEs are configured to operate based on CRS-based transmissionmodes, time division multiplexing (TDM) partitioning with one region ofa single frequency network (SFN) and one region of pico cell splittingfor high geometry legacy UEs may be used. This may enable a basic formof “cell” splitting for UEs located in close proximity to a specificpoint. In the aforementioned setup, for UEs configured with transmissionmodes that rely on UE-specific reference signals for demodulation, thedata transmission may be based on UE-specific DM-RS.

When the network is configured with different cell IDs, a heterogeneousnetwork design may be used. That is, eICIC techniques, including but notlimited to the techniques specified as part of LTE Rel-10, may beemployed. It is further possible to configure UEs to operate withtransmission modes that rely on UE-specific DM-RS, similar to theaforementioned same cell ID configuration.

To resolve any issues with respect to radio resource management(RRM)/radio link management (RLM), when the network is configured withdifferent cell IDs, for LTE Rel-8/9, the UE may attach to a strongestcell, which is similar to a heterogeneous network design with collidingCRS. For LTE Rel-10 and later, existing procedures may work ifinterference cancellation (IC) or advanced receiver processing isavailable. Hence, there may be no need for sounding reference signals(SRS)-based association to points. The control signals and data signalsmay also be decoupled.

When the network is configured with the same cell ID, CRS transmissionfrom the points transmitting CRS combine, which may be transparent toUEs. The UEs may be configured to transmit sounding reference signals(SRS) to determine the proximity of the UEs to certain points. It mayalso be possible to use reference signals other than the CRS for RRM/LLMprocedures, e.g., the CSI-RS may be used for such purposes.

With respect to feedback/codebook consideration, UEs may perform channelstate information reporting based at least in part on the CSI-RS andprovide CSI feedback for a network configured with the same cell ID.However, an issue arises because existing codebooks were designedassuming that a path loss for each of the CSI-RS is equal, and maytherefore suffer some performance loss if this condition is notsatisfied. Since multiple RRHs may comprise a single CSI-RS resourcefrom a UE's perspective, the path loss associated with each of theCSI-RS ports may be different. As such, codebook refinements may beneeded to enable efficient cross-point CSI feedback that takes intoaccount the proper path losses to points. Multiple CSI feedback may beprovided by grouping antenna ports and providing feedback per group.

For CRS-based CSI feedback, the network configured with the same cell IDsees a composite channel. Therefore, some degradation may occur asexisting codebooks were not devised to account for such a setup. ForCSI-RS based CSI feedback, CSI-RS is used for channel feedback. Someperformance difference between same cell ID/different cell ID setups mayresult if interference estimation is based on CRS. Performing bothchannel and interference measurement based on CSI-RS may also bepossible.

Further considering feedback/codebooks, when the network is configuredwith different cell IDs, precoding matrix indicator (PMI)/rank index(RI) feedback characteristics may differ. For example, PMI/RI feedbackmay be provided for a strongest cell based on CRS. Alternatively, PMI/RIfeedback may be based on CSI-RS for a certain transmission mode.Notably, the CSI-RS configuration is UE specific, so the UE canassociate freely with RRHs as desired. Codebooks may also be enhanced toprovide for inter-cell PMI/RI feedback, etc.

When the network is configured with the same cell ID, PMI/RI feedbackcharacteristics may also differ. For example, PMI/RI feedback may beprovided assuming transmission from all points using CRS. PMI/RIfeedback may also be based on CSI-RS for a certain transmission mode.Because the CSI-RS configuration is UE specific, the UE can associatefreely with RRHs or have a cross-point assignment. However, the existingcodebooks may not be designed for cross-point assignment of CSI-RSports.

With respect to channel quality indicator (CQI) feedback, when thenetwork is configured with different cell IDs, CQI/RI feedbackcharacteristics may differ. For example, CQI/RI feedback may be the sameas in a heterogeneous network design with colliding CRS.

When the network is configured with the same cell ID, CQI/RI feedbackcharacteristics may also differ. For example, CQI/RI feedback may dependon CRS configuration (e.g., whether all points transmit CRS or only themacro node transmits CRS). If all points transmit CRS, then CQI/RIfeedback may be the same as in a single SFN case. Channel estimation maybe based on CSI-RS, and interference estimation may be performed usingCSI-RS. Therefore, CQI/RI feedback may be based on CSI-RS.

In an aspect, the term transmission/reception point (“TxP”) or pointrepresents geographically separated transmission/reception nodes whichare being controlled by at least one central entity (e.g., eNB) and mayhave the same cell ID or different cell IDs. The exemplaryconfigurations are applicable to macro node/RRH configurations with thesame cell ID or different cell IDs. In the case of different cell IDs,CRS transmissions may be configured to overlap, which leads to a similarscenario as the same cell ID case. However, the case of different cellIDs may be advantageous as system characteristics which depend on thecell ID (e.g., scrambling sequences, etc.) may be more easilydifferentiated by the UE.

An exemplary macro node/RRH entity provides for separation of controltransmissions and data transmissions within the coverage of a macronode/RRH configuration. Referring to an aspect of FIG. 8, when the cellID is the same for each TxP, the PDCCH may be transmitted with CRS fromthe macro node 802 or both the macro node 802 and the RRHs 804, 806,808, 810, while the PDSCH may be transmitted with CSI-RS and DM-RS froma subset of the TxPs. Referring to another aspect of FIG. 8, when thecell ID is different for some of the TxPs, PDCCH may be transmitted withCRS in each cell ID group. The CRS transmitted from each cell ID groupmay or may not collide. UEs cannot differentiate CRS transmitted frommultiple TxPs with the same cell ID, but can differentiate CRStransmitted from multiple TxPs with different cell IDs (e.g., usinginterference cancellation or similar techniques).

The separation of control transmissions and data transmissions withinthe coverage of a macro node/RRH configuration provides for aUE-transparent way of “associating” UEs with at least one point for datatransmission while transmitting control based on CRS transmissions fromall the points. This enables cell splitting for a data transmissionacross different points while leaving the control channel common. Theterm “associating” above refers to configuring antenna ports for aspecific UE for a data transmission. This is different from anassociation that would be performed in the context of handover. Controlinformation may be transmitted based on CRS as discussed supra.Separating control and data may allow for a faster reconfiguration ofthe antenna ports that are used for a UE's data transmission comparedwith reconfiguration via a handover process. Cross-point feedback may bepossible by configuring a UE's antenna ports to correspond to thephysical antennas of different points.

The separation of control transmissions and data transmissions withinthe coverage of a macro node/RRH configuration is enabled by UE-specificreference signals. CSI-RS and DM-RS are the reference signals used inthe LTE-A context. Interference estimation may be performed based onCSI-RS muting. Because control transmissions are common, controlcapacity issues may exist because PDCCH capacity may be limited.Accordingly, control capacity may be enlarged by using a frequencydivision multiplexed (FDM) control channel. Moreover, a relay PDCCH(R-PDCCH) or extensions thereof may be used to supplement, augment, orreplace the PDCCH control channel.

The UE provides CSI feedback based at least in part on its CSI-RSconfiguration to provide PMI/RI/CQI. Typical codebook design assumesthat antennas are not geographically separated, and therefore, the samepath loss exists from the antenna array to the UE. However, this is notthe case for multiple RRHs, as the antennas are uncorrelated and seedifferent channels. Therefore, codebooks may be refined to enable moreefficient cross-point CSI feedback. For example, CSI estimation maycapture the path loss difference between antenna ports associated withdifferent points. Furthermore, multiple feedback may be provided bygrouping antenna ports and provide feedback per group.

With respect to CRS-based transmission modes as well as PDCCH controlchannels (e.g., considering legacy UE operation), in case of same cellID operation, the macro node and RRHs transmit the same data and thesame control information at the same time. In case different cell IDsare used for RRHs, some cell splitting is possible for CRS-based dataand/or control transmissions. UE-RS of releases prior to LTE Rel-10 maybe used for demodulation and enables some cell splitting. As CSI-RS maynot be available for some UEs (e.g., UEs of releases prior to Rel-10),CSI feedback could be based on reciprocity-based feedback. For example,the eNB can determine the channel conditions based on sounding referencesignals (SRS) transmitted from the UEs.

It should be noted that the network setup with the same cell IDs maybenefit mobility procedures due to the combining of CRS transmissions.This may result in a decreased number of handovers.

In the case of a macro node/RRH configuration with different cell IDs,separation of control transmissions and data transmissions is possiblesimilar to the case of a macro node/RRH configuration with the same cellID (as mentioned supra). While a UE may receive control information fromthe strongest cell, or possibly a certain set of strongcells/transmission points, data transmissions may be performed from adifferent set of cells or transmission points. In one example, this mayavoid the need to decode control information from the set ofcells/transmission points that are performing data transmission, whichmay possibly have a weaker signal for their control transmissions.

In the case of the macro node/RRH configuration with different cell IDs,control information may therefore be received from the strongest cell,or possibly from a set of cells with a strong signal. Therefore, UEslocated in close proximity to one or multiple RRHs may be able toreceive control information from those transmission points directly.This may have advantages in terms of control capacity compared to thescenario in which all nodes share the same cell ID.

In another aspect, relating to the macro node/RRH configuration withdifferent cell IDs, a UE in the coverage area of a stronger cell ondownlink, which may possibly include one or more transmission pointsthat share the same cell ID, may receive data from a different set oftransmission points. Thus, the data sent from these transmissions pointsmay need to appear as data sent from the stronger cell. For UE-RS/DM-RSbased transmissions, the sequences may be scrambled for this purpose. Onuplink, the UE may use the scrambling sequence assigned by the strongercell. Moreover, the uplink control may be received by the transmissionpoints that are transmitting data as they are likely closer to the UE.

In another aspect, again primarily relating to the macro node/RRHconfiguration with different cell IDs, a cell may transmit multipleCSI-RS for the same antenna on different locations corresponding todifferent cell IDs. This will allow a neighboring eNB to advertise theCSI-RS of this cell as the CSI-RS of the neighboring eNB. This may beuseful, for example, for Rel-10 UEs that connect to the macro node forcontrol information but need a feedback channel as measured from theCSI-RS of a pico node/RRH with a different cell ID. The pico node/RRHmay transmit CSI-RS using a scrambling sequence corresponding to a macrocell ID in addition to its own CSI-RS using scrambling based on its owncell ID.

In another aspect, it may be beneficial to increase the number ofUE-RS/DM-RS scrambling sequences for a given cell ID to make pilotsindependent when multiple RRHs sharing the same cell ID transmit datausing UE-RS at the same time. The scrambling sequences for UE-RS/DM-RSshould be assigned such that the same sequence is most likely used byRRHs that are far away from each other. More generally, the scramblingsequences used can be planned across the cell and RRHs to reduce theimpact of SFN having the same pilot scrambling.

In another aspect, an RRH at the cell edge may perform rangeexpansion/data transmissions for more than one cell. This isstraightforward when neighboring cells have colliding CRS. For example,if the RRH does not transmit CRS, the RRH could rate match on someresources corresponding to the CRS location of one eNB for one set ofUEs (e.g., UEs connected to the first cell) while rate matching based onthe CRS location of the second eNB on other resources or for other UEs,etc. Alternatively, the RRH could transmit CRS corresponding to one cellID but transmit data to UEs of a second cell on MBSFN subframes of thecell using the first cell ID.

In a further aspect, with respect to a UE-specific configuration ofCSI-RS ports, the CSI-RS patterns agreed to in LTE Rel-10 may beexploited to improve the CSI estimation accuracy for UEs by assigningCSI-RS patterns judiciously throughout the macro node/RRH configuration.It should be appreciated that this is possible for both the macronode/RRH configuration with the same cell ID and macro node/RRHconfiguration with different cell IDs.

FIG. 10 is a flow chart 1000 of a method of wireless communication. Themethod allows for the separation of control transmissions and datatransmissions within the coverage area of a macro node and a pluralityof geographically displaced remote radio heads (RRHs) coupled to themacro node. The macro node together with the RRHs may be considered aplurality of transmission/reception points (TxPs) or points.Accordingly, the separation of control transmissions and datatransmissions allows for association of a UE with at least one TxP fordata transmission while control information is transmitted based on CRStransmissions from a potentially different set of TxPs or even all theTxPs. This enables cell splitting for data transmissions acrossdifferent TxPs while potentially leaving control transmissions common toall TxPs. The method may be performed by an eNB.

At step 1002, control information is transmitted with common referencesignals (CRS) to a UE from a first subset of points. CRS may betransmitted in every downlink subframe and in every resource block inthe frequency domain, thus covering an entire cell bandwidth. The UE mayuse the CRS for channel estimation for coherent demodulation of adownlink physical channel except for a physical multicast channel (PMCH)and for PDSCH in the case of transmission modes 7, 8, or 9. The UE mayalso use the CRS to acquire channel state information (CSI). Also, UEmeasurements on CRS may be used as the basis for cell selection andhandover decisions.

At step 1004, data is sent to the UE based on UE-specific referencesignals (e.g., demodulation reference signals (DM-RS)) from a secondsubset of points. The DM-RS are intended to be used by the UE for PDSCHchannel estimation in transmission modes 7, 8, or 9. These referencesignals are “UE-specific” as they are intended to be used for channelestimation by a designated UE or specific designated subset of UEs.Thus, a UE-specific reference signal is only transmitted within resourceblocks assigned for PDSCH transmission to the designated UE(s).

Referring to FIG. 10, the first subset of points may have the same cellidentifier, and therefore, each may transmit the same controlinformation and CRS. Alternatively, a designated point in the pluralityof points may have a different cell identifier from any other point inthe plurality of point. Accordingly, in an aspect, second controlinformation and a second CRS may be transmitted from the designatedpoint, wherein the designated point is not in the first subset ofpoints.

Still referring to FIG. 10, the control information may be transmittedusing a frequency division multiplexed (FDM) control channel or a relaychannel. The relay channel may be a relay physical downlink controlchannel (R-PDCCH). Furthermore, the first subset of points may includethe macro node and zero or more RRHs, while the second subset of pointsmay include the macro node and/or one or more RRHs.

At step 1006, channel state information reference signals (CSI-RS) aresent to the UE from the second subset of points. CSI-RS is specificallyintended to be used by the UE to acquire CSI in the case whendemodulation reference signals (DM-RS) are used for channel estimation.For example, CSI-RS is used in the case of transmission mode 9. CSI-RShave a significantly lower time/frequency density, thus implying lessoverhead, compared to CRS.

At step, 1008, feedback based at least in part on the CSI-RS is receivedfrom the UE. The received feedback may be a channel state informationreport comprising at least one of precoding matrix indicator (PMI), rankindex (RI), or channel quality indicator (CQI) feedback. Moreover, thereceived PMI, RI, or CQI feedback may be based on channel conditionsfrom the second subset of points to the UE and interference conditionsat the UE.

FIG. 11 is a flow chart 1100 of a method of wireless communication. Themethod allows for the separation of control transmissions and datatransmissions within the coverage area of a macro node and a pluralityof geographically displaced remote radio heads (RRHs) coupled to themacro node, similar to the method of FIG. 10 described above. The macronode together with the RRHs may be considered a plurality oftransmission/reception points (TxPs) or points. The method of FIG. 11also allows for reciprocity-based feedback, wherein the UE provideschannel state information to the macro node/RRHs in the absence ofCSI-RS from the RRHs. The method may be performed by an eNB.

At step 1102, control information is transmitted with common referencesignals (CRS) to a UE from a first subset of points. As discussed supra,the UE may use CRS for channel estimation for coherent demodulation of adownlink physical channel except for a physical multicast channel (PMCH)and for PDSCH in the case of transmission modes 7, 8, or 9. The UE mayalso use the CRS to acquire channel state information (CSI). Also, UEmeasurements on CRS may be used as the basis for cell selection andhandover decisions.

At step 1104, data is sent to the UE based on UE-specific referencesignals (e.g. demodulation reference signals (DM-RS)) from a secondsubset of points. The UE-specific reference signals are “UE-specific”and are intended to be used for channel estimation by a designated UE orspecific designated subset of UEs. Thus, a UE-specific reference signalis only transmitted within resource blocks assigned for PDSCHtransmission to the designated UE(s).

At step 1106, a sounding reference signal (SRS) is received from the UEat one or more points of the plurality of points. SRS may be transmittedon the uplink to allow the eNB to estimate the uplink channel state atdifferent frequencies. The channel-state estimates can then, forexample, be used by a network scheduler to assign resource blocks foruplink PUSCH transmission (uplink channel-dependent scheduling), as wellas to select different transmission parameters such as an instantaneousdata rate and different parameters related to uplink multi-antennatransmission. SRS may also be used for uplink timing estimation and toestimate downlink channel conditions assuming downlink/uplink channelreciprocity. Also at step 1106, channel quality indicator (CQI) feedbackmay be received from the UE.

At step 1108, the eNB may determine channel strengths based on thereceived SRS. Channel strength may depend on a distance between a senderand receiver. Therefore, the eNB may determine channel strengths at eachof the one or more points from the UE based on the SRS received by theone or more points.

At step 1110, the eNB determines a modulation and coding scheme (MCS)for a future data transmission to the UE. The MCS is determined based onthe determined channel strengths and the received CQI from the UE.Thereafter, at step 1112, the eNB modulates and codes the data fortransmission to the UE based on the determined MCS.

FIG. 12 is a flow chart 1200 of a method of wireless communication. Themethod allows for the separation of control transmissions and datatransmissions within the coverage area of a macro node and a pluralityof geographically displaced remote radio heads (RRHs) coupled to themacro node, similar to the method of FIG. 10 described above. The macronode together with the RRHs may be considered a plurality oftransmission/reception points (TxPs) or points. The method of FIG. 12also allows for a UE in close proximity to a point, to receive databased on CRS from that point without use of UE-specific referencesignals. The method may be performed by an eNB.

At step 1202, control information is transmitted with common referencesignals (CRS) to a UE from a subset of points. As discussed supra, theUE may use the CRS for channel estimation for coherent demodulation of adownlink physical channel except for a physical multicast channel (PMCH)and for PDSCH in the case of transmission modes 7, 8, or 9. The UE mayalso use the CRS to acquire channel state information (CSI). Also, UEmeasurements on CRS may be used as the basis for cell selection andhandover decisions.

At step 1204, a sounding reference signal (SRS) is received from the UEat one or more points of the plurality of points. SRS may be transmittedon the uplink to allow the eNB to estimate the uplink channel state atdifferent frequencies. The channel-state estimates can then, forexample, be used by a network scheduler to assign resource blocks foruplink PUSCH transmission (uplink channel-dependent scheduling), as wellas to select different transmission parameters such as an instantaneousdata rate and different parameters related to uplink multi-antennatransmission. SRS may also be used for uplink timing estimation and toestimate downlink channel conditions assuming downlink/uplink channelreciprocity.

At step 1206, the eNB may determine channel strengths based on thereceived SRS. Channel strength may depend on a distance between a senderand receiver. Therefore, the eNB may determine channel strengths at eachof the one or more points from the UE based on the SRS received by theone or more points.

At step 1208, the eNB determines whether the UE is in close proximity toat least one point of the one or more points based on the determinedchannel strengths. If so, the eNB may save resources and operate moreefficiently by sending data to the UE from the at least one point inclose proximity to the UE.

At step 1210, based on the result of step 1208, the eNB proceeds to senddata to the UE based on CRS from the at least one point in closeproximity to the UE. Here, in contrast with the methods of FIGS. 10 and11, the data is sent to the UE based on reference signals that are notUE-specific. That is, the reference signals are not intended for channelestimation by a designated UE or specific designated subset of UEs.Moreover, the data transmission based on CRS is sent to the UE from theat least one point independent of data transmissions from points not inclose proximity to the UE. Accordingly, cell splitting may beaccomplished without use of UE-specific reference signals.

FIG. 13 is a flow chart 1300 of a method of wireless communication. Themethod allows for the separation of control transmissions and datatransmissions within the coverage area of a macro node and a pluralityof geographically displaced remote radio heads (RRHs) coupled to themacro node. The macro node together with the RRHs may be considered aplurality of transmission/reception points (TxPs) or points.Accordingly, the separation of control transmissions and datatransmissions allows for association of a UE with at least one TxP fordata transmission while control information is transmitted based on CRStransmissions from a potentially different set of TxPs or even all theTxPs. This enables cell splitting for data transmissions acrossdifferent TxPs while potentially leaving control transmissions common toall TxPs. The method may be performed by a UE.

At step 1302, the UE receives control information with common referencesignals (CRS) from a first subset of points. The first subset of pointsmay include the macro node and zero or more RRHs. As discussed supra,the UE may use the CRS for channel estimation for coherent demodulationof a downlink physical channel except for a physical multicast channel(PMCH) and for PDSCH in the case of transmission modes 7, 8, or 9. TheUE may also use the CRS to acquire channel state information (CSI).Also, UE measurements on CRS may be used as the basis for cell selectionand handover decisions.

At step 1304, the UE receives data based on UE-specific referencesignals (e.g., demodulation reference signals (DM-RS)) from a secondsubset of points. The second subset of points may include one or moreRRHs. The DM-RS are specifically intended to be used by the UE forchannel estimation for PDSCH in transmission modes 7, 8, or 9. Thesereference signals are “UE-specific” as they are intended to be used forchannel estimation by a designated UE or specific designated subset ofUEs. Thus, a UE-specific reference signal is only transmitted withinresource blocks assigned for PDSCH transmission to the designated UE(s).

At step 1306, the UE may receive an identifier from the first subset ofpoints. Here, the plurality of points may be configured with differentcell identifiers. Thus, the received identifier may be different from acell identifier associated with the first subset of points. Accordingly,the UE may utilize knowledge of the different identifier to decode datareceived from a point. Hence, at step 1308, the UE descrambles thereceived data from the second subset of points based on the identifierreceived from the first subset of points.

At step 1310, the UE receives channel state information referencesignals (CSI-RS) from the second subset of points. As discussed supra,CSI-RS is specifically intended to be used by the UE to acquire CSI inthe case when demodulation reference signals (DM-RS) are used forchannel estimation. For example, CSI-RS is used in the case oftransmission mode 9. CSI-RS have a significantly lower time/frequencydensity, thus implying less overhead, compared to CRS.

At step, 1312, the UE transmits feedback based at least in part on thereceived CSI-RS. The transmitted feedback may be a channel stateinformation report including at least one of precoding matrix indicator(PMI), rank index (RI), or channel quality indicator (CQI) feedback.Moreover, the transmitted PMI, RI, or CQI feedback may be based onchannel/interference conditions from the second subset of points to theUE and interference conditions at the UE.

FIG. 14 is a conceptual data flow diagram 1400 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 106. The exemplary apparatus 106 may include a plurality oftransmission/reception points (TxPs) or points, such as a macro node anda plurality of geographically displaced remote radio heads (RRHs)coupled to the macro node. The apparatus 106 includes a receiving module1402 that receives various signals 1418, such as UE feedback, soundingreference signals (SRS) and a channel quality indicator (CQI), forexample. The apparatus also includes various modules that processsignals received by the receiving module 1402, such as a channelstrength determination module 1404, a modulation and coding scheme (MCS)determination module 1406, a modulating and coding module 1408, acontrol, data, and reference signal (CDR) generation module 1410, and aproximity determination module 1414. The apparatus further includes asending module 1412 that transmits or sends various signals 1416, suchas control information, data, CRS, UE-RS, and CSI-RS, for example.

In an aspect, the CDR generation module 1410 may generate controlinformation and transmit the control information with common referencesignals (CRS) to a UE from a first subset of points via the sendingmodule 1412. The CDR generation module 1410 may also generate data andsend the data to the UE based on UE-specific reference signals (e.g.,demodulation reference signals (DM-RS)) from a second subset of pointsvia the sending module 1412. The CDR generation module 1410 may furthergenerate channel state information reference signals (CSI-RS) and sendthe CSI-RS to the UE from the second subset of points via the sendingmodule 1412. The receiving module 1402 may receive feedback, such as achannel state information report, based at least in part on the CSI-RSfrom the UE. The channel state information report may include precodingmatrix indicator (PMI), rank index (RI), or channel quality indicator(CQI) feedback.

In another aspect, the receiving module 1402 may receive a soundingreference signal (SRS) and channel quality indicator (CQI) feedback fromthe UE at one or more points of the plurality of points. The receivingmodule 1402 may send the received SRS to the channel strengthdetermination module 1404, wherein the channel strength determinationmodule 1404 may determine channel strengths at each of the one or morepoints from the UE based on the received SRS. The MCS determinationmodule 1406 may determine a modulation and coding scheme (MCS) for datato be transmitted to the UE based on the channel strengths determined bythe channel strength determination module 1404 and the CQI received bythe receiving module 1402. Thereafter, based on the MCS determined bythe MCS determination module 1406, the modulating and coding module 1408modulates and codes the data to be transmitted.

In a further aspect, the CDR generation module 1410 may generate controlinformation and transmit the control information with CRS to the UE froma subset of points via the sending module 1412. Moreover, the receivingmodule 1402 may receive a sounding reference signal (SRS) from the UE atone or more points of the plurality of points. The receiving module 1402may send the received SRS to the channel strength determination module1404, wherein the channel strength determination module 1404 maydetermine channel strengths at each of the one or more points from theUE based on the received SRS. Based on the determined channel strengths,the proximity determination module 1414 may determine whether the UE isin close proximity to at least one point of the one or more points.Thereafter, if the UE is determined to be in close proximity to the atleast one point, the CDR generation module 1410 may send a datatransmission based on CRS to the UE from the at least one point via thesending module 1412. The sending module 1412 may send the datatransmission based on CRS to the UE from the at least one pointindependent of data transmissions from points not in close proximity tothe UE.

In yet another aspect, the CDR generation module 1410 may generatesecond control information and transmit the control information with asecond CRS to a UE from a designated point via the sending module 1412.The designated point may be a point in a plurality of points but not inthe first subset of points. Also, the designated point may have adifferent cell identifier from any other point in the plurality ofpoints.

FIG. 15 is a conceptual data flow diagram 1500 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 102. The exemplary apparatus 102 communicates with a pluralityof transmission/reception points (TxPs) or points, such as a macro nodeand a plurality of geographically displaced remote radio heads (RRHs)coupled to the macro node. The apparatus 102 includes a receiving module1502 that receives various signals 1512, such as control information,data, an identifier, CRS, UE-RS, and CSI-RS, for example. The apparatusalso includes various modules that process signals received by thereceiving module 1502, such as a data descrambling module 1504, acontrol, data, and reference signal (CDR) processing module 1506, and achannel state determination and report generation module 1508. Theapparatus further includes a sending module 1510 that transmits or sendsvarious signals 1514 including feedback information, for example.

In an aspect, the receiving module 1502 may receive control informationwith common reference signals (CRS) from a first subset of points. Thereceiving module 1502 may also receive data based on UE-specificreference signals (e.g., demodulation reference signals (DM-RS)) from asecond subset of points. Any control information, data, or referencesignals received by the receiving module 1502 may be sent to the CDRprocessing module 1506 for further processing. The CDR processing module1506 may then send the control information, data, and/or referencesignals to the channel state determination and report generation module1508 to determine a channel state.

In another aspect, the receiving module 1502 may receive an identifierfrom the first subset of points, wherein the identifier is differentfrom a cell identifier associated with the first subset of points.Accordingly, the data descrambling module 1504 may descramble the datareceived from the second subset of points based on the identifierreceived by the receiving module 1502. Thereafter, the data descramblingmodule 1504 may send the descrambled data to the CDR processing module1506 for further processing.

In a further aspect, the receiving module 1502 may receive channel stateinformation reference signals (CSI-RS) from the second subset of points,and sends the received CSI-RS to the CDR processing module 1506. Basedon information received from the CDR processing module 1506, the channelstate determination and report generation module 1508 may determine achannel state and generates a channel state information report. Thechannel state information report may include at least one of precodingmatrix indicator (PMI), rank index (RI), or channel quality indicator(CQI) feedback. The channel state determination and report generationmodule 1508 may also receive the CSI-RS from the CDR processing module1508. Thereafter, the channel state determination and report generationmodule 1508 may transmit the channel state information report based onthe CSI-RS via the sending module 1510.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow charts FIGS. 10-13. Assuch, each step in the aforementioned flow charts FIGS. 10-13 may beperformed by a module and the apparatus may include one or more of thosemodules. The modules may be one or more hardware components specificallyconfigured to carry out the stated processes/algorithm, implemented by aprocessor configured to perform the stated processes/algorithm, storedwithin a computer-readable medium for implementation by a processor, orsome combination thereof.

FIG. 16 is a diagram illustrating an example of a hardwareimplementation for an apparatus 106′ employing a processing system 1614.The processing system 1614 may be implemented with a bus architecture,represented generally by the bus 1624. The bus 1624 may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system 1614 and the overall designconstraints. The bus 1624 links together various circuits including oneor more processors and/or hardware modules, represented by the processor1604, the modules 1402, 1404, 1406, 1408, 1410, 1412, 1414, and thecomputer-readable medium 1606. The bus 1624 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1614 may be coupled to a transceiver 1610. Thetransceiver 1610 is coupled to one or more antennas 1620. Thetransceiver 1610 provides a means for communicating with various otherapparatus over a transmission medium. The processing system 1614includes a processor 1604 coupled to a computer-readable medium 1606.The processor 1604 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1606. Thesoftware, when executed by the processor 1604, causes the processingsystem 1614 to perform the various functions described supra for anyparticular apparatus. The computer-readable medium 1606 may also be usedfor storing data that is manipulated by the processor 1604 whenexecuting software. The processing system further includes at least oneof the modules 1402, 1404, 1406, 1408, 1410, 1412, and 1414. The modulesmay be software modules running in the processor 1604, resident/storedin the computer readable medium 1606, one or more hardware modulescoupled to the processor 1604, or some combination thereof. Theprocessing system 1614 may be a component of the eNB 610 and may includethe memory 676 and/or at least one of the TX processor 616, the RXprocessor 670, and the controller/processor 675.

In one configuration, the apparatus 106/106′ for wireless communicationincludes means for transmitting control information with commonreference signals (CRS) to a user equipment (UE) from a first subset ofthe points, means for sending a data transmission based on UE-specificreference signals (e.g., demodulation reference signals (DM-RS)) to theUE from a second subset of the points, means for transmitting secondcontrol information and a second CRS from a designated point, thedesignated point being a point in a plurality of points but not in thefirst subset of points, and the designated point having a different cellidentifier from any other point in the plurality of points, means fortransmitting channel state information reference signals (CSI-RS) to theUE from the second subset of points, means for receiving a channel stateinformation report from the UE based at least in part on the CSI-RS, thechannel state information report comprising at least one of precodingmatrix indicator (PMI), rank index (RI), or channel quality indicator(CQI) feedback, means for receiving a sounding reference signal (SRS)from the UE at one or more points of the plurality of points, means fordetermining channel strengths at each of the one or more points from theUE based on the SRS received by the one or more points, means forreceiving channel quality indicator (CQI) feedback from the UE, meansfor determining a modulation and coding scheme (MCS) based on thedetermined channel strengths and the CQI, and means for modulating andcoding the data based on the MCS.

In another configuration, the apparatus 106/106′ for wirelesscommunication includes means for transmitting control information withcommon reference signals (CRS) to a user equipment (UE) from a subset ofpoints, means for receiving a sounding reference signal (SRS) from theUE at one or more points of the plurality of points, means fordetermining channel strengths to each of the one or more points from theUE based on the SRS received by the one or more points, means fordetermining whether the UE is in close proximity to at least one pointof the one or more points based on the determined channel strengths, andmeans for sending a data transmission based on CRS to the UE from the atleast one point when the UE is determined to be in close proximity tothe at least one point based on the determined channel strengths,wherein the data transmission based on CRS is sent to the UE from the atleast one point independent of data transmissions from points not inclose proximity to the UE.

The aforementioned means may be one or more of the aforementionedmodules of the apparatus 106 and/or the processing system 1614 of theapparatus 106′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1614 mayinclude the TX Processor 616, the RX Processor 670, and thecontroller/processor 675. As such, in one configuration, theaforementioned means may be the TX Processor 616, the RX Processor 670,and the controller/processor 675 configured to perform the functionsrecited by the aforementioned means.

FIG. 17 is a diagram illustrating an example of a hardwareimplementation for an apparatus 102′ employing a processing system 1714.The processing system 1714 may be implemented with a bus architecture,represented generally by the bus 1724. The bus 1724 may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system 1714 and the overall designconstraints. The bus 1724 links together various circuits including oneor more processors and/or hardware modules, represented by the processor1704, the modules 1502, 1504, 1506, 1508, 1510, and thecomputer-readable medium 1706. The bus 1724 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1714 may be coupled to a transceiver 1710. Thetransceiver 1710 is coupled to one or more antennas 1720. Thetransceiver 1710 provides a means for communicating with various otherapparatus over a transmission medium. The processing system 1714includes a processor 1704 coupled to a computer-readable medium 1706.The processor 1704 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1706. Thesoftware, when executed by the processor 1704, causes the processingsystem 1714 to perform the various functions described supra for anyparticular apparatus. The computer-readable medium 1706 may also be usedfor storing data that is manipulated by the processor 1704 whenexecuting software. The processing system further includes at least oneof the modules 1502, 1504, 1506, 1508, and 1510. The modules may besoftware modules running in the processor 1704, resident/stored in thecomputer readable medium 1706, one or more hardware modules coupled tothe processor 1704, or some combination thereof. The processing system1714 may be a component of the UE 650 and may include the memory 660and/or at least one of the TX processor 668, the RX processor 656, andthe controller/processor 659.

In one configuration, the apparatus 102/102′ for wireless communicationincludes means for receiving control information with common referencesignals (CRS) from a first subset of points, means for receiving datatransmitted based on user equipment (UE)-specific reference signals(e.g., demodulation reference signals (DM-RS)) from a second subset ofpoints, means for receiving channel state information reference signals(CSI-RS) from the second subset of points, means for transmitting achannel state information report based on the received CSI-RS, thechannel state information report comprising at least one of precodingmatrix indicator (PMI), rank index (RI), or channel quality indicator(CQI) feedback, means for receiving an identifier from the first subsetof points, the identifier being different from a cell identifierassociated with the first subset of points, and means for descramblingthe received data from the second subset of points based on the receivedidentifier. The aforementioned means may be one or more of theaforementioned modules of the apparatus 102 and/or the processing system1714 of the apparatus 102′ configured to perform the functions recitedby the aforementioned means. As described supra, the processing system1714 may include the TX Processor 668, the RX Processor 656, and thecontroller/processor 659. As such, in one configuration, theaforementioned means may be the TX Processor 668, the RX Processor 656,and the controller/processor 659 configured to perform the functionsrecited by the aforementioned means.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Further, somesteps may be combined or omitted. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed as a means plus functionunless the element is expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of a macro node and at least one remoteradio head (RRH) coupled to the macro node, the macro node and the atleast one RRH comprising a plurality of points that are geographicallydisplaced within a cell of the macro node, the method comprising:configuring, using one or more processors, channel state informationreference signals (CSI-RS) for a user equipment (UE) to performinterference estimation; transmitting, using the one or more processors,control information and common reference signals (CRS) associated with afirst cell identifier to the UE from a first subset of points that aregeographically displaced within the cell of the macro node; and sending,using the one or more processors, the CSI-RS and a data transmissionassociated with a second cell identifier to the UE from a second subsetof points that are geographically displaced within the cell of the macronode, the second subset of points being configured to use ports within agroup of ports when sending the CSI-RS to the UE, wherein each of thesecond subset of points sends the CSI-RS to the UE on different portswithin the group of ports, wherein the first cell identifier isdifferent than the second cell identifier.
 2. The method of claim 1,wherein the first subset of points has the same cell identifier and eachpoint in the first subset of points transmits the same controlinformation and CRS.
 3. The method of claim 1, further comprising:transmitting second control information and a second CRS from adesignated point, the designated point being a point in the plurality ofpoints but not in the first subset of points, and the designated pointhaving a different cell identifier from any other point in the pluralityof points.
 4. The method of claim 1, further comprising receiving achannel state information report from the UE based at least in part onthe CSI-RS, the channel state information report comprising at least oneof precoding matrix indicator (PMI), rank index (RI), or channel qualityindicator (CQI) feedback.
 5. The method of claim 4, wherein the receivedchannel state information report, comprising PMI, RI, or CQI feedback,is based on channel conditions from the second subset of points to theUE and interference conditions at the UE.
 6. The method of claim 1,wherein the control information is transmitted using at least one of afrequency division multiplexed (FDM) control channel or a relay physicaldownlink control channel (R-PDCCH).
 7. The method of claim 1, whereinthe first subset of points comprises the macro node and zero or moreRRHs, and the second subset of points comprises the macro node and/orone or more RRHs.
 8. The method of claim 1, further comprising:receiving a sounding reference signal (SRS) from the UE at one or morepoints of the plurality of points; determining channel strengths at eachof the one or more points from the UE based on the SRS received by theone or more points; receiving channel quality indicator (CQI) feedbackfrom the UE; determining a modulation and coding scheme (MCS) based onthe determined channel strengths and the CQI; and modulating and codingthe data based on the MCS.
 9. A method of a user equipment (UE)communicating with a macro node and at least one remote radio head (RRH)coupled to the macro node, the macro node and the at least one RRHcomprising a plurality of points that are geographically displacedwithin a cell of the macro node, the method comprising: receiving, usingone or more processors, control information and a common referencesignal (CRS) associated with a first cell identifier from a first subsetof points that are geographically displaced within the cell of the macronode; receiving, using the one or more processors, data transmittedbased on UE-specific demodulation reference signals (DM-RS) associatedwith a second cell identifier from a second subset of points that aregeographically displaced within the cell of the macro node; receiving,using the one or more processors, channel state information referencesignals (CSI-RS) from the second subset of points, the second subset ofpoints being configured to use ports within a group of ports whensending the CSI-RS to the UE, wherein each of the second subset ofpoints sends the CSI-RS to the UE on different ports within the group ofports; performing, using the one or more processors, interferenceestimation based on CSI-RS; and transmitting, using the one or moreprocessors, a channel state information report based at least in part onthe received first CSI-RS, the channel state information reportcomprising at least one of precoding matrix indicator (PMI), rank index(RI), or channel quality indicator (CQI) feedback, wherein the firstcell identifier is different than the second cell identifier.
 10. Themethod of claim 9, wherein the first subset of points comprises themacro node and zero or more RRHs, and the second subset of pointscomprises the macro node and/or one or more RRHs.
 11. The method ofclaim 9, further comprising: receiving an identifier from the firstsubset of points, the identifier being different from a cell identifierassociated with the first subset of points; and descrambling thereceived data from the second subset of points based on the receivedidentifier.
 12. The method of claim 9, wherein the transmitted channelstate information report, comprising PMI, RI, or CQI feedback, is basedon channel conditions from the second subset of points to the UE andinterference conditions at the UE.
 13. An apparatus for wirelesscommunication comprising a plurality of points that are geographicallydisplaced within a cell of a macro node, the plurality of pointscomprising the macro node and a plurality of remote radio heads (RRHs)coupled to the macro node, the apparatus further comprising: means forconfiguring channel state information reference signals (CSI-RS) for auser equipment (UE) to perform interference estimation; means fortransmitting control information and common reference signals (CRS)associated with a first cell identifier to the UE from a first subset ofpoints that are geographically displaced within the cell of the macronode; and means for sending the CSI-RS and a data transmissionassociated with a second cell identifier to the UE from a second subsetof points that are geographically displaced within the cell of the macronode, the second subset of points being configured to use ports within agroup of ports when sending the CSI-RS to the UE, wherein each of thesecond subset of points sends the CSI-RS to the UE on different portswithin the group of ports, wherein the first cell identifier isdifferent than the second cell identifier.
 14. The apparatus of claim13, wherein the first subset of points has a same cell identifier andeach point in the first subset of points transmits the same controlinformation and CRS.
 15. The apparatus of claim 13, further comprising:means for transmitting second control information and a second CRS froma designated point, the designated point being a point in the pluralityof points but not in the first subset of points, and the designatedpoint having a different cell identifier from any other point in theplurality of points.
 16. The apparatus of claim 13, further comprisingmeans for receiving a channel state information report from the UE basedat least in part on the CSI-RS, the channel state information reportcomprising at least one of precoding matrix indicator (PMI), rank index(RI), or channel quality indicator (CQI) feedback.
 17. The apparatus ofclaim 16, wherein the received channel state information report,comprising PMI, RI, or CQI feedback, is based on channel conditions fromthe second subset of points to the UE and interference conditions at theUE.
 18. The apparatus of claim 13, wherein the control information istransmitted using at least one of a frequency division multiplexed (FDM)control channel or a relay physical downlink control channel (R-PDCCH).19. The apparatus of claim 13, wherein the first subset of pointscomprises the macro node and zero or more RRHs, and the second subset ofpoints comprises the macro node and/or one or more RRHs.
 20. Theapparatus of claim 13, further comprising: means for receiving asounding reference signal (SRS) from the UE at one or more points of theplurality of points; means for determining channel strengths at each ofthe one or more points from the UE based on the SRS received by the oneor more points; means for receiving channel quality indicator (CQI)feedback from the UE; means for determining a modulation and codingscheme (MCS) based on the determined channel strengths and the CQI; andmeans for modulating and coding the data based on the MCS.
 21. Anapparatus for wireless communication, the apparatus communicating with aplurality of points that are geographically displaced within a cell of amacro node, the plurality of points comprising the macro node and aplurality of remote radio heads (RRHs) coupled to the macro node, theapparatus comprising: means for receiving control information and acommon reference signal (CRS) associated with a first cell identifierfrom a first subset of points that are geographically displaced withinthe cell of the macro node; means for receiving data transmitted basedon UE-specific demodulation reference signals (DM-RS) associated with asecond cell identifier from a second subset of points that aregeographically displaced within the cell of the macro node; means forreceiving channel state information reference signals (CSI-RS) from thesecond subset of points, the second subset of points being configured touse ports within a group of ports when sending the CSI-RS to the UE,wherein each of the second subset of points sends the CSI-RS to the UEon different ports within the group of ports; and means for transmittinga channel state information report based at least in part on thereceived first CSI-RS, the channel state information report comprisingat least one of precoding matrix indicator (PMI), rank index (RI), orchannel quality indicator (CQI) feedback, wherein the first cellidentifier is different than the second cell identifier.
 22. Theapparatus of claim 21, wherein the first subset of points comprises themacro node and zero or more RRHs, and the second subset of pointscomprises the macro node and/or one or more RRHs.
 23. The apparatus ofclaim 21, further comprising: means for receiving an identifier from thefirst subset of points, the identifier being different from a cellidentifier associated with the first subset of points; and means fordescrambling the received data from the second subset of points based onthe received identifier.
 24. The apparatus of claim 21, wherein thetransmitted channel state information report, comprising PMI, RI, or CQIfeedback, is based on channel conditions from the second subset ofpoints to the UE and interference conditions at the UE.
 25. An apparatusfor wireless communication comprising a plurality of points that aregeographically displaced within a cell of a macro node, the plurality ofpoints comprising the macro node and a plurality of remote radio heads(RRHs) coupled to the macro node, the apparatus further comprising: amemory; and a processing system coupled to the memory and configured to:configure channel state information reference signals (CSI-RS) for auser equipment (UE) to perform interference estimation; transmit controlinformation and common reference signals (CRS) associated with a firstcell identifier to the UE from a first subset of points that aregeographically displaced within the cell of the macro node; and send theCRI-RS and a data transmission associated with a second cell identifierto the UE from a second subset of points that are geographicallydisplaced within the cell of the macro node, the second subset of pointsbeing configured to use ports within a group of ports when sending theCSI-RS to the UE, wherein each of the second subset of points sends theCSI-RS to the UE on different ports within the group of ports, whereinthe first cell identifier is different than the second cell identifier.26. The apparatus of claim 25, wherein the first subset of points has asame cell identifier and each point in the first subset of pointstransmits the same control information and CRS.
 27. The apparatus ofclaim 25, wherein the processing system is further configured to:transmit second control information and a second CRS from a designatedpoint, the designated point being a point in the plurality of points butnot in the first subset of points, and the designated point having adifferent cell identifier from any other point in the plurality ofpoints.
 28. The apparatus of claim 25, wherein the processing system isfurther configured to receive a channel state information report fromthe UE based at least in part on the CSI-RS, the channel stateinformation report comprising at least one of precoding matrix indicator(PMI), rank index (RI), or channel quality indicator (CQI) feedback. 29.The apparatus of claim 28, wherein the received channel stateinformation report, comprising PMI, RI, or CQI feedback, is based onchannel conditions from the second subset of points to the UE andinterference conditions at the UE.
 30. The apparatus of claim 25,wherein the control information is transmitted using at least one of afrequency division multiplexed (FDM) control channel or a relay physicaldownlink control channel (R-PDCCH).
 31. The apparatus of claim 25,wherein the first subset of points comprises the macro node and zero ormore RRHs, and the second subset of points comprises the macro nodeand/or one or more RRHs.
 32. The apparatus of claim 25, wherein theprocessing system is further configured to: receive a sounding referencesignal (SRS) from the UE at one or more points of the plurality ofpoints; determine channel strengths at each of the one or more pointsfrom the UE based on the SRS received by the one or more points; receivechannel quality indicator (CQI) feedback from the UE; determine amodulation and coding scheme (MCS) based on the determined channelstrengths and the CQI; and modulate and code the data based on the MCS.33. An apparatus for wireless communication, the apparatus communicatingwith a plurality of points that are geographically displaced within acell of a macro node, the plurality of points comprising the macro nodeand a plurality of remote radio heads (RRHs) coupled to the macro node,the apparatus comprising: a memory; and a processing system coupled tothe memory and configured to: receive control information and a commonreference signal (CRS) associated with a first cell identifier from afirst subset of points that are geographically displaced within the cellof the macro node; receive data transmitted based on UE-specificdemodulation reference signals (DM-RS) associated with a second cellidentifier from a second subset of points that are geographicallydisplaced within the cell of the macro node; receive channel stateinformation reference signals (CSI-RS) from the second subset of points,the second subset of points being configured to use ports within a groupof ports when sending the CSI-RS to the UE, wherein each of the secondsubset of points sends the CSI-RS to the UE on different ports withinthe group of ports; perform interference estimation based on CSI-RS; andtransmit a channel state information report based at least in part onthe received first CSI-RS, the channel state information reportcomprising at least one of precoding matrix indicator (PMI), rank index(RI), or channel quality indicator (CQI) feedback, wherein the firstcell identifier is different than the second cell identifier.
 34. Theapparatus of claim 33, wherein the first subset of points comprises themacro node and zero or more RRHs, and the second subset of pointscomprises the macro node and/or one or more RRHs.
 35. The apparatus ofclaim 33, wherein the processing system is further configured to:receive an identifier from the first subset of points, the identifierbeing different from a cell identifier associated with the first subsetof points; and descramble the received data from the second subset ofpoints based on the received identifier.
 36. The apparatus of claim 33,wherein the transmitted channel state information report, comprisingPMI, RI, or CQI feedback, is based on channel conditions from the secondsubset of points to the UE and interference conditions at the UE.
 37. Anon-transitory computer-readable medium for communicating with aplurality of points that are geographically displaced within a cell of amacro node, the plurality of points comprising the macro node and aplurality of remote radio heads (RRHs) coupled to the macro node, thecomputer-readable medium comprising code for: configuring channel stateinformation reference signals (CSI-RS) for a user equipment (UE) toperform interference estimation; transmitting control information andcommon reference signals (CRS) associated with a first cell identifierto the UE from a first subset of points that are geographicallydisplaced within the cell of the macro node; and sending the CSI-RS anda data transmission associated with a second cell identifier to the UEfrom a second subset of points that are geographically displaced withinthe cell of the macro node, the second subset of points being configuredto use ports within a group of ports when sending the CSI-RS to the UE,wherein each of the second subset of points sends the CSI-RS to the UEon different ports within the group of ports, wherein the first cellidentifier is different than the second cell identifier.
 38. Thenon-transitory computer-readable medium of claim 37, wherein the firstsubset of points has a same cell identifier and each point in the firstsubset of points transmits the same control information and CRS.
 39. Thenon-transitory computer-readable medium of claim 37, wherein the firstsubset of points comprises the macro node and zero or more RRHs, and thesecond subset of points comprises the macro node and/or one or moreRRHs.
 40. The non-transitory computer-readable medium of claim 37,further comprising code for: receiving a sounding reference signal (SRS)from the UE at one or more points of the plurality of points;determining channel strengths at each of the one or more points from theUE based on the SRS received by the one or more points; receivingchannel quality indicator (CQI) feedback from the UE; determining amodulation and coding scheme (MCS) based on the determined channelstrengths and the CQI; and modulating and coding the data based on theMCS.
 41. A non-transitory computer-readable medium for communicatingwith a plurality of points that are geographically displaced within acell of a macro node, the plurality of points comprising the macro nodeand a plurality of remote radio heads (RRHs) coupled to the macro node,the computer-readable medium comprising code for: receiving controlinformation and a common reference signal (CRS) associated with a firstcell identifier from a first subset of points that are geographicallydisplaced within the cell of the macro node; receiving data transmittedbased on UE-specific demodulation reference signals (DM-RS) associatedwith a second cell identifier from a second subset of points that aregeographically displaced within the cell of the macro node; receivingchannel state information reference signals (CSI-RS) from the secondsubset of points, the second subset of points being configured to useports within a group of ports when sending the CSI-RS to the UE, whereineach of the second subset of points sends the CSI RS to the UE ondifferent ports within the group of ports by the second subset of ports;performing interference estimation based on the CSI-RS; and transmittinga channel state information report based at least in part on thereceived first CSI-RS, the channel state information report comprisingat least one of precoding matrix indicator (PMI), rank index (RI), orchannel quality indicator (CQI) feedback, wherein the first cellidentifier is different than the second cell identifier.
 42. Thenon-transitory computer-readable medium of claim 41, wherein the firstsubset of points comprises the macro node and zero or more RRHs, and thesecond subset of points comprises the macro node and/or one or moreRRHs.
 43. The non-transitory computer-readable medium of claim 41,further comprising code for: receiving an identifier from the firstsubset of points, the identifier being different from a cell identifierassociated with the first subset of points; and descrambling thereceived data from the second subset of points based on the receivedidentifier.